TWI499696B - Pretreating agent for electroplating, pretreatment method for electroplating, and electroplating method - Google Patents

Description

Pretreatment agent for electroplating, pretreatment method for electroplating, and electroplating method

The present invention relates to a pretreatment agent for electroplating and a pretreatment method for electroplating, which is preferably used for a printed circuit board (particularly, a photoresist (ink or dry film) for forming a circuit is applied to a copper layer) Treatment, and also related to the plating method.

The printed circuit board includes a double-sided printed circuit board and a multilayer printed circuit board in which via holes and through vias are used to form interlayer circuits. The via hole and the via hole are subjected to electroless copper plating to form an interlayer connection, and the photoresist layer is formed on the surface of the substrate to form an electrical circuit. Thereafter, the substrate is pretreated and electrolytic copper plating is performed to ensure that the copper film has a copper thickness as a conductive material.

The photoresist is specifically designed to be stripped under alkaline conditions. Therefore, the pretreatment agents used in the pretreatment of copper plating are mostly neutral or acidic, especially acidic. Typically, existing acidic pretreatment agents contain a surfactant and an inorganic or organic acid. Acidic pretreatment agents are typically used to impart to or through-hole wettability or to remove dust or scum from the copper or copper alloy surface prior to electrolytic copper plating.

Depending on the chemical in the development of the photoresist, cleaning, uneven drying, etc., the substrate copper film (electroless copper plating film or copper foil) used to form the circuit is subjected to surface oxidation reaction, and the resulting oxide damages the electrolytic copper plating film and the substrate. Adhesion between copper layers.

It is considered that the existing acidic pretreatment agent has a weak cleaning effect on the oxide film on the copper surface. Therefore, in order to obtain a better cleaning effect, there is a demand for developing a pretreatment agent for strongly removing an oxide film. However, excessive cleaning may deteriorate the adhesion between the substrate copper and the photoresist, which may cause the photoresist to peel off.

Further, the related art reference materials related to the present invention include Japanese Patent No. 2,604,632, JP-A H3-191077, JP-A 2001-089882, Japanese Patent No. 4208826, JP-A 2009-132967, JP-A H10 -212593, JP-A 2005-113162, Japanese Patent No. 4409951, JP-A 2005-333104, and JP-A 2000-104177.

Therefore, there is a need for a pretreatment agent for electroplating which does not impair the adhesion between the substrate copper and the photoresist and the adhesion between the substrate copper and the electrolytic copper plating film, and is used for electroplating using a pretreatment agent. There are also needs for pretreatment methods and electroplating methods using pretreatment methods.

In order to satisfy the foregoing needs, the inventors conducted sufficient and extensive research. As a result of their research, the inventors have found that the anti-adsorbent component having a slight adverse effect on the aforementioned adhesion is adsorbed on the surface of the substrate before the component of the rinse photoresist has a significant adverse effect on the adhesion, and thereafter The above requirements can be met when cleaning is not too strong, instead of being considered as essential for intense cleaning. Based on this finding, the present invention has been completed.

Accordingly, the present invention provides a pretreatment agent for electroplating, a pretreatment method for electroplating, and a plating method, which are characterized as follows.

The pretreatment agent for electroplating of the present invention is characterized in that it comprises an aqueous solution containing the following basic components:

(A) at least one anti-adsorbent selected from the group consisting of a triazole compound, a pyrazole compound, an imidazole compound, a cationic surfactant, and a zwitterionic surfactant;

(B) Chloride ion.

In the pretreatment agent for electroplating, preferably, the component (A) is at least one selected from the group consisting of a cationic surfactant and a zwitterionic surfactant. More preferably, the component (A) is a zwitterionic surfactant.

Further, in the pretreatment agent for electroplating, preferably, the aqueous solution further contains (C) a nonionic surfactant.

In the pretreatment agent for electroplating, preferably, the aqueous solution further contains (D) at least one solvent selected from the group consisting of water-soluble ethers, amines, alcohols, glycol ethers, ketones, esters, and fatty acids. More preferably, the component (D) comprises at least one solvent selected from the group consisting of water-soluble ethers, alcohols, ketones, esters, and fatty acids.

Further, in the pretreatment agent for electroplating, preferably, the aqueous solution further contains (E) an acid.

In the pretreatment agent for electroplating, preferably, the aqueous solution further contains (F) an oxidizing agent.

The pretreatment method for electroplating of the present invention is characterized in that it comprises immersing the workpiece in the aforementioned pretreatment agent for electroplating.

In the pretreatment method for electroplating, preferably, the workpiece is immersed in the pretreatment agent for electroplating, and ultrasonic treatment is simultaneously performed. Alternatively, when the workpiece is immersed, electrolytic treatment is also performed.

The plating method of the present invention is characterized by using the aforementioned pretreatment method for electroplating.

Advantageous effects of the present invention

The pretreatment agent for electroplating of the present invention does not impair the adhesion between the substrate copper and the photoresist, and does not impair the adhesion between the substrate copper and the electrolytic copper plating film.

The invention will now be described in detail below.

The pretreatment agent for electroplating according to the present invention includes an aqueous solution containing the following basic components:

(A) at least one anti-adsorbent selected from the group consisting of a triazole compound, a pyrazole compound, an imidazole compound, a cationic surfactant, and a zwitterionic surfactant;

(B) Chloride ion.

(A) anti-adsorbent

The anti-adsorbent (A) in the present invention is first adsorbed on the surface of the metal, thereby limiting the adsorption of the component of the rinse photoresist on the metal surface. The anti-adsorbent (A) in the present invention is a triazole compound, a pyrazole compound, an imidazole compound, a cationic surfactant, and a zwitterionic surfactant, which may be used singly or in combination of two or more thereof. The molecular weight of the component (A) of the present invention (in the case of a polymer means a weight average molecular weight) is preferably at most 1,000, particularly in the range of from 60 to 900.

Specific examples of the triazole compound include triazole, benzotriazole, methylbenzotriazole, aminotriazole, aminobenzotriazole, and hydroxybenzotriazole. Specific examples of the pyrazole compound include pyrazole, dimethylpyrazole, phenylpyrazole, methylphenylpyrazole, and aminopyrazole. Specific examples of the imidazole compound include imidazole, methylimidazole, and phenylimidazole.

Examples of the cationic surfactant include an alkyltrimethylammonium type, a dialkyldimethylammonium type, a trialkylmethylammonium type, a tetraalkylammonium type, a benzyl type, a pyridinium type, a diammonium type, or an amine salt type. . Examples of the zwitterionic surfactant include an amine oxide type, a betaine type, an imidazoline type, an aminodiacetic acid type, an aniline type, a glycerin type, a sulfate type, a sulfonate type, or a phosphate type.

When the triazole compound, the pyrazole compound or the imidazole compound is used as the component (A) of the present invention, the concentration thereof is preferably from 0.01 to 200 g/liter, particularly from 0.05 to 10 g/liter. If the concentration is less than 0.01 g/liter, the amount of adsorption is too small, and the effects of the present invention cannot be obtained successfully. On the other hand, if the concentration exceeds 200 g/liter, the photoresist is peeled off and the economy is lowered.

When a cationic surfactant or a zwitterionic surfactant is used as the component (A) of the present invention, the concentration thereof is preferably from 0.01 to 200 g/liter, particularly from 0.5 to 10 g/liter. If the concentration is less than 0.01 g/liter, the amount of adsorption is too small, and the effects of the present invention cannot be obtained successfully. On the other hand, if the concentration exceeds 200 g/liter, the photoresist is peeled off and the economy is lowered. Further, a commercially available product can be used as the cationic surfactant and the zwitterionic surfactant.

(B) chloride ion

The chloride ion (B) of the present invention is adsorbed around the metal grains considered to promote the uniformity of the cleaning performance of the metal surface. Examples of the compound for supplying chloride ions include hydrochloric acid, ammonium chloride, sodium chloride, potassium chloride, a cationic surfactant containing a chloride ion (including a cationic dye), and an oxychloride, but not limited thereto. . Further, the compound for supplying chloride ions may be used singly or in combination of two or more.

The concentration of chloride ions in the pretreatment agent according to the invention is preferably from 0.01 to 200 g/l, especially from 0.04 to 100 g/l, more particularly from 0.2 to 50 g/l. If the concentration is less than 0.01 g/liter, the desired cleaning effect cannot be obtained. On the other hand, if the concentration exceeds 200 g/liter, the substrate copper is tarnished and the economy is lowered.

In the present invention, the components (A) and (B) coexist, which effectively enhances the adhesion of the copper film deposited by electroplating performed in the next step. This effect is derived from the fact that component (A) limits the adsorption and composition of the components of the rinse photoresist on the metal surface and (B) effectively cleans the surface of the substrate having copper, thereby enhancing the copper-copper adhesion.

(C) nonionic surfactant

The pretreatment agent according to the present invention preferably contains (C) a nonionic surfactant in addition to the component (A) and the component (B). This nonionic surfactant enhances the wettability of the workpiece, thereby enhancing the adsorption and cleaning effects. Examples of nonionic surfactants include alkyl ethers, alkylphenyl ethers, alkylamines, alkylguanamines, polyhydric alcohol ethers, fatty acid esters, POE polyhydric alcohol fatty acid esters, polyhydric alcohol fatty acids Ester, ethylene glycol, or a polyalkylene oxide or polyethylene oxide surfactant having an average HLB of 10 to 18. A commercially available product can be used as the nonionic surfactant.

When this nonionic surfactant is used, its concentration is preferably from 0.1 to 200 g/liter, particularly from 0.5 to 10 g/liter. If the concentration is less than 0.1 g/liter, the desired wettability cannot be obtained. On the other hand, if the concentration exceeds 200 g/liter, the photoresist is peeled off and the economy is lowered.

Further, when a cationic surfactant and a zwitterionic surfactant are used as the component (A), if sufficient wettability has been secured, it is not necessary to add the component (C).

(D) solvent

The pretreatment agent according to the present invention preferably contains (D) a solvent in addition to the aforementioned components. This solvent can be used as an auxiliary agent for cleaning the substrate copper. Examples of the component (D) solvent include water-soluble ethers, amines, alcohols, glycol ethers, ketones, esters, and fatty acids. In particular, preferred examples include ethers (e.g., dioxane, tetrahydrofuran, etc.), amines (e.g., ethylamine, ethanolamine, N-methyl-2-pyrrolidone, N,N-dimethylformamide, etc.), alcohols (such as methanol, ethanol, propanol, ethylene glycol, propylene glycol, etc.), ethanol ether (such as ethyl cellosolve, butyl cellosolve, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, propylene glycol monoethyl ether, etc.) , ketones (such as acetone, methyl ethyl ketone, butyrolactone, etc.), esters (such as ethyl acetate, propyl acetate, butyl acetate, acetate cellosolve, etc.), and fatty acids (such as propionic acid, butyric acid, formic acid) , acetic acid, lactic acid, etc.). Further, these solvents may be used singly or in combination of two or more.

When the solvent is added, the concentration thereof is preferably from 0.01 to 200 g/liter, particularly from 0.1 to 50 g/liter. If the concentration is less than 0.01 g/liter, the cleaning performance cannot be improved. On the other hand, if the concentration exceeds 200 g/liter, the photoresist is peeled off and the economy is lowered.

(E) acid

The pretreatment agent according to the present invention preferably contains (E) an acid in addition to the aforementioned components. This acid enhances the removal effect of the oxide film present on the metal. This acid can be an inorganic or organic acid. Examples of the inorganic acid include sulfuric acid, nitric acid, hydrofluoric acid, and phosphoric acid. Examples of the organic acid include citric acid, formic acid, lactic acid, and alkylsulfonic acid. These acids may be used singly or in combination of two or more.

When the pretreatment agent according to the present invention contains the acid, the concentration of the acid in the pretreatment agent is preferably from 0.1 to 200 g/liter, particularly from 1 to 100 g/liter. If the concentration is less than 0.1 g/liter, the effect of removing the oxide film cannot be obtained. On the other hand, if the concentration exceeds 200 g/liter, the photoresist is peeled off and the economy is lowered.

Further, the use of hydrochloric acid as a source of (B) chloride ion or the addition of a fatty acid as the solvent (D), and if the acid concentration is within the above-mentioned appropriate range, it is not necessary to add the component (E).

(F) oxidant

The pretreatment agent according to the present invention preferably contains (F) an oxidizing agent in addition to the aforementioned components. This oxidizing agent can be used as an auxiliary agent for cleaning the substrate copper. Examples of the oxidizing agent include peroxide, ferric chloride, copper chloride, and aqueous hydrogen peroxide, but are not limited thereto. Further, the oxidizing agent may be used singly or in combination of two or more.

When the oxidizing agent is added, its concentration is preferably from 0.01 to 200 g/liter, particularly from 1 to 50 g/liter. If the concentration is less than 0.01 g/liter, the effect of promoting cleaning cannot be obtained. On the other hand, if the concentration exceeds 200 g/liter, the substrate copper is tarnished and the economy is lowered.

The pretreatment agent according to the present invention is suitably used for pretreatment of a surface of a substrate copper layer (electroless copper plating film or copper foil) of a printed circuit board (the surface of which is formed by copper plating to form a copper film), the printed circuit board having A photoresist (ink or dry film) and a photoresist pattern of the circuit are formed by forming an electrolytic copper plating film on the copper layer of the substrate by copper plating. As a pretreatment method, preferably, in the method employed, the workpiece is immersed in the pretreatment solvent according to the present invention. When the pretreatment for electroplating is carried out using the pretreatment agent according to the present invention, the treatment temperature is preferably from 25 to 50 ° C, particularly from 30 to 45 ° C. If the pretreatment temperature is lower than 25 ° C, the cleaning is insufficient. On the other hand, if the temperature is higher than 50 ° C, peeling of the photoresist occurs.

Further, the pretreatment is preferably carried out for 1 to 30 minutes, particularly 2 to 10 minutes. If the processing time is less than 1 minute, sufficient cleaning effect cannot be obtained. On the other hand, if the time exceeds 30 minutes, the peeling of the photoresist is initiated.

Depending on the water washing conditions of the photoresist development step and the degree of unevenness of the drying, the oxide film formed on the surface of the copper substrate may be hard, and it may damage the adhesion between the substrate copper and the electrolytic copper plating film formed thereon. . In this case, preferably, the ultrasonic treatment is performed while immersing the workpiece in the pretreatment agent according to the present invention. Ultrasonic processing is used in conjunction with pretreatment to improve cleaning performance. Ultrasonic processing can be performed at 26 to 42 kHz for 1 to 3 minutes.

In the case where the oxide film on the surface of the substrate copper is hard and the adhesion between the substrate copper and the electrolytic copper plating film is damaged, it is also possible to perform electrolytic treatment while immersing the workpiece in the pretreatment agent according to the present invention. method. Electrolysis treatment during the pretreatment period can improve cleaning performance. The electrolytic treatment can be carried out by direct current cation electrolysis, and using copper or stainless steel as a cathode, at 0.1 to 5 volts or using a cation current density of 0.5 to 1 ampere/square inch for 1 to 3 minutes.

In the electroplating method according to the present invention, electroplating is performed after pretreating the workpiece by using the pretreatment agent according to the present invention. This plating method is suitably applied to copper plating. When the plating method is carried out, a conventional known plating bath and plating conditions can be used.

Instance

Now, the present invention will be described in a specific manner by way of examples and comparative examples, but the invention is not limited to the examples.

A substrate obtained by adhering a photoresist film to a substrate R-1705 manufactured by Panasonic Electric Works Co., Ltd. was used as an evaluation substrate. As a photoresist film, Sunfort (ADH252) manufactured by Asahi Kasei E-materials Corp. or Photec (RY-3525) manufactured by Hitachi Chemical Co., Ltd. was used. The line/space was set to 25 μm / 25 μm, and the film thickness of the electrolytic copper plating film was set to 20 μm.

Examples 1-24, Comparative Examples 1-18

The pretreatment agent was prepared in the compositions shown in Tables 2 to 5 below. Adhesion evaluation was performed according to the following method. In addition, in Tables 2 to 5, the units are in grams per liter.

Evaluation of adhesion between substrate copper and photoresist

The substrate for evaluation with a photoresist film adhered to the substrate was immersed in a pretreatment agent and pretreated at 35 ° C for 3 minutes. The evaluation substrate thus treated was observed under an optical microscope (magnification 200 times) to evaluate the presence/absence of peeling of the photoresist. When the peeling of the photoresist was not present, it was evaluated as good adhesion; when the peeling of the photoresist was present, it was evaluated as poor adhesion. The results are also shown in Tables 2 to 5. In Tables 2 to 5, the symbol ○ represents good adhesion, and the symbol x represents poor adhesion.

Evaluation of adhesion between substrate copper and coating

According to the procedure shown in Table 1 below, the substrate which had been subjected to the plating treatment was immersed in a 40 g/liter NaOH solution at 50 ° C for 5 minutes, and the photoresist was stripped. When the evaluation substrate is enlarged under an optical microscope (magnification 200 times), as shown in FIG. 1, the cutting edge of the cutting blade 4 is directed toward the substrate side between the copper wires deposited at L/S = 25 μm / 25 μm. The pressure is pressed until it comes into contact with the substrate copper 2, and the plating film 3 is turned up in the horizontal direction. Further, reference numeral 1 in Fig. 1 denotes a substrate. When the substrate copper was peeled off together with the plating film so that the resin located below was exposed, it was evaluated that the adhesion was good; when only the plating film was peeled off, the substrate copper was exposed, and the adhesion was evaluated as poor. The results of the assessment are also shown in Tables 2 to 5. In Tables 2 to 5, the symbol ○ represents good adhesion, and the symbol x represents poor adhesion.

From the results of Examples 1 to 12, it was found that the pretreatment agent composed of the anti-adsorbent and the chloride ion had good adhesion.

From the results of Examples 13 to 24, it was found that in addition to the anti-adsorbent and the chloride ion, the nonionic surfactant, the acid, the solvent, and the oxidizing agent were also contained in the pretreatment agent, and good adhesion was also obtained.

In Comparative Example 16, the acidic pretreatment agent commonly used in the related art was used, and the adhesion between the substrate copper and the plating film was poor. From the results of Comparative Examples 1 to 5 and 8 to 14, it was found that when a solution having a single composition was used, the adhesion between the substrate copper and the plating film was poor. From the results of Comparative Examples 6 and 7, it was found that the addition of a bromide ion or a fluorine ion in place of the chloride ion resulted in poor adhesion between the substrate copper and the plating film. From the results of Comparative Example 15, in which the microetching solution composition commonly used in the related art was used, it was found that the microetching caused poor adhesion between the substrate copper and the plating film. From the results of Comparative Example 17, it was found that the absence of chloride ions resulted in poor adhesion between the substrate copper and the plating film. From the results of Comparative Example 18, it was found that the absence of the anti-adsorbent resulted in poor adhesion between the substrate copper and the plating film.

Example 25-28

Using the pretreatment agent of Example 1, the adhesion evaluation was carried out in the same manner as the above method, but the pretreatment was carried out at a treatment temperature of 25, 30, 45, or 50 °C. The results are shown in Table 6. The adhesion between the substrate copper and the resistive agent and the adhesion between the substrate copper and the plating film are good.

Example 29-33

Using the pretreatment agent of Example 1, the adhesion evaluation was performed in the same manner as the foregoing method, but the pretreatment time was 1, 5, 10, 20, or 30 minutes. The results are shown in Table 7. The adhesion between the substrate copper and the resistive agent and the adhesion between the substrate copper and the plating film are good.

Reference example 1

The evaluation substrate was treated at 120 ° C for 2 hours before the pretreatment step shown in Table 1 was carried out to oxidize the surface of the substrate. Thereafter, the adhesion between the substrate copper and the plating film was carried out using the pretreatment agent of Example 1 and according to the aforementioned method. The results are shown in Table 8.

Example 34

The adhesion between the substrate copper and the plating film was evaluated in the same manner as in the foregoing method, except that the substrate was subjected to heat treatment at 120 ° C for 2 hours before the substrate was subjected to the pretreatment step shown in Table 1 to oxidize the surface of the substrate, and then the substrate was evaluated. Ultrasonic treatment was carried out while immersing in the pretreatment agent of Example 1 in the pretreatment step shown in Table 1. The results are shown in Table 8.

Example 35

The adhesion between the substrate copper and the plating film was evaluated in the same manner as in the foregoing method, except that the substrate was subjected to heat treatment at 120 ° C for 2 hours before the substrate was subjected to the pretreatment step shown in Table 1 to oxidize the surface of the substrate, and then the substrate was evaluated. The electrolytic treatment (0.5 volt) was carried out while immersing in the pretreatment agent of Example 1 in the pretreatment step shown in Table 1. The results are shown in Table 8.

From the results of Reference Example 1, it was found that the oxide film on the surface of the substrate caused a partial adhesion defect. From Examples 34 and 35, it is seen that when an oxide film is present on the surface of the substrate, ultrasonic treatment or electrolytic treatment is combined with pretreatment to solve the problem of poor adhesion.

1. . . Substrate

2. . . Substrate copper

3. . . Coating

4. . . Cutting knife

Figure 1 illustrates a method for evaluating the adhesion between a substrate copper and a coating in an example.

1. . . Substrate

2. . . Substrate copper

3. . . Coating

4. . . Cutting knife

Claims (11)

A pretreatment agent for electroplating, comprising an aqueous solution comprising: (A) at least one anti-adsorbent selected from the group consisting of a triazole compound, a pyrazole compound, and an imidazole compound; and (B) a chloride ion; and (C) a nonionic interface An active agent; wherein the concentration of the component (A) is 0.01 to 200 g/liter, the concentration of the component (B) is 001 to 200 g/liter, and the concentration of the component (C) is 0.1 to 200 g / liter. The pretreatment agent for electroplating according to claim 1, wherein the aqueous solution further contains (D) at least one solvent selected from the group consisting of water-soluble ethers, amines, alcohols, glycol ethers, ketones, esters, and fatty acids. The pretreatment agent for electroplating according to item 2 of the patent application, wherein the component (D) comprises at least one solvent selected from the group consisting of water-soluble ethers, alcohols, ketones, esters, and fatty acids. The pretreatment agent for electroplating according to claim 1, wherein the aqueous solution further contains (E) an acid. The pretreatment agent for electroplating according to claim 1, wherein the aqueous solution further contains (F) an oxidizing agent. A pretreatment method for electroplating, comprising immersing a workpiece in an application In the pretreatment agent for electroplating according to item 1 of the patent scope. A pretreatment method for electroplating, which comprises immersing a workpiece in a pretreatment agent for electroplating according to item 1 of the patent application, and performing ultrasonic treatment at the same time. A pretreatment method for electroplating, comprising immersing a workpiece in a pretreatment agent for electroplating according to item 1 of the patent application, and performing electrolytic treatment at the same time. An electroplating method in which a pretreatment method for electroplating as in claim 6 of the patent application is used. An electroplating method in which a pretreatment method for electroplating as in claim 7 of the patent application is used. An electroplating method in which a pretreatment method for electroplating as in the eighth aspect of the patent application is used.